linux-kernel - Re: [PATCH v1 5/5] ASoC: tegra: ahub: Reset hardware properly

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Message-ID: <c2f3d149-0781-3d0a-1d68-f6820386e84d@gmail.com>
Date:   Mon, 18 Jan 2021 03:02:38 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Jonathan Hunter <jonathanh@...dia.com>,
        Sameer Pujar <spujar@...dia.com>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Takashi Iwai <tiwai@...e.com>,
        Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 5/5] ASoC: tegra: ahub: Reset hardware properly

15.01.2021 18:44, Thierry Reding пишет:
> On Tue, Jan 12, 2021 at 03:58:34PM +0300, Dmitry Osipenko wrote:
>> Assert hardware reset before clocks are enabled and then de-assert it
>> after clocks are enabled. This brings hardware into a predictable state
>> and removes relying on implicit de-assertion of resets which is done by
>> the clk driver.
>>
>> Tested-by: Peter Geis <pgwipeout@...il.com>
>> Tested-by: Nicolas Chauvet <kwizart@...il.com>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>>  sound/soc/tegra/tegra30_ahub.c | 33 ++++++++++++++++-----------------
>>  sound/soc/tegra/tegra30_ahub.h |  1 +
>>  2 files changed, 17 insertions(+), 17 deletions(-)
>>
>> diff --git a/sound/soc/tegra/tegra30_ahub.c b/sound/soc/tegra/tegra30_ahub.c
>> index 4dbb58f7ea36..246cf6a373a1 100644
>> --- a/sound/soc/tegra/tegra30_ahub.c
>> +++ b/sound/soc/tegra/tegra30_ahub.c
>> @@ -65,10 +65,20 @@ static int tegra30_ahub_runtime_resume(struct device *dev)
>>  {
>>  	int ret;
>>  
>> +	ret = reset_control_assert(ahub->reset);
>> +	if (ret)
>> +		return ret;
>> +
>>  	ret = clk_bulk_prepare_enable(ahub->nclocks, ahub->clocks);
>>  	if (ret)
>>  		return ret;
>>  
>> +	ret = reset_control_reset(ahub->reset);
>> +	if (ret) {
>> +		clk_bulk_disable_unprepare(ahub->nclocks, ahub->clocks);
>> +		return ret;
>> +	}
>> +
>>  	regcache_cache_only(ahub->regmap_apbif, false);
>>  	regcache_cache_only(ahub->regmap_ahub, false);
>>  
>> @@ -462,7 +472,6 @@ static int tegra30_ahub_probe(struct platform_device *pdev)
>>  {
>>  	const struct of_device_id *match;
>>  	const struct tegra30_ahub_soc_data *soc_data;
>> -	struct reset_control *rst;
>>  	struct resource *res0;
>>  	void __iomem *regs_apbif, *regs_ahub;
>>  	int ret = 0;
>> @@ -475,22 +484,6 @@ static int tegra30_ahub_probe(struct platform_device *pdev)
>>  		return -EINVAL;
>>  	soc_data = match->data;
>>  
>> -	/*
>> -	 * The AHUB hosts a register bus: the "configlink". For this to
>> -	 * operate correctly, all devices on this bus must be out of reset.
>> -	 * Ensure that here.
>> -	 */
>> -	rst = of_reset_control_array_get_exclusive(pdev->dev.of_node);
>> -	if (IS_ERR(rst)) {
>> -		dev_err(&pdev->dev, "Can't get reset: %p\n", rst);
>> -		return PTR_ERR(rst);
>> -	}
>> -
>> -	ret = reset_control_deassert(rst);
>> -	reset_control_put(rst);
>> -	if (ret)
>> -		return ret;
>> -
>>  	ahub = devm_kzalloc(&pdev->dev, sizeof(struct tegra30_ahub),
>>  			    GFP_KERNEL);
>>  	if (!ahub)
>> @@ -507,6 +500,12 @@ static int tegra30_ahub_probe(struct platform_device *pdev)
>>  	if (ret)
>>  		return ret;
>>  
>> +	ahub->reset = devm_reset_control_array_get_exclusive(&pdev->dev);
>> +	if (IS_ERR(ahub->reset)) {
>> +		dev_err(&pdev->dev, "Can't get reset: %p\n", ahub->reset);
> 
> I didn't notice that the prior patch already introduced this, but I'd
> prefer for this to either be %pe so that the symbolic error name is
> printed, or %ld with PTR_ERR(ahub->reset) to format this in a more
> standard way that can be more easily grepped for and parsed.

This is already fixed in v2. Good catch anyways, thanks.

> It also seems like the prior patch that converts this to use
> of_reset_control_array_get_exclusive() is a bit pointless now. Why not
> just move to this directly instead?

These are two independent changes. The previous patch fixed the missing
resets, this patch changes the hardware initialization logic.